Liquid revolution counter for fuze arming

ABSTRACT

A safing and arming apparatus for use in a spinning projectile in which after a predetermined number of revolutions of the projectile a rotor is unbalanced by the relocation of liquid within the rotor thus causing the rotor to rotate and bring a detonator in line with a firing train.

United States Pateqt n 1 Egli et a1. I I

M lMarch 20, 1973 54] LIQUID REVOLUTION COUNTER FOR FUZE ARMINGInventors: Werner Hans Egli; Asbjorn M. Severson, both of Minneapolis, Minn.

[73] Assignee: Honeywell Inc., Minneapolis, Minn.

[22] Filed: June 1, 1971 [21] Appl. No.: 148,460

[52] U.S. Cl. ..I02/79, 102/78, 102/81 [51] -Int. Cl. ..F42c 15/26 [58]Field of Search ..l02/78, 79, 80, 70, 81

[56] I References Cited UNITED STATES PATENTS 2,641,186 6/1953 Apotheloz..l02/79 2,331,633 Spooner ..l02/79 2,588,424 3/1952 Speaker 102/702 R2,703,071 3/1955 Sooth 102/80 3,001,044 9/1961 Brown ....l02/70.2 R

3,075,465 1/1963 Craig ..102/80 X 3,425,354 2/1969 Carlson 102/79Primary Examiner-Samuel W. Engle Attorney-Charles J. Ungemach, AlbinMedved and Alan G. Carlson [57] ABSTRACT V W V A safing and armingapparatus for use in a spinning projectile in which after apredetermined number of revolutions of the projectile a rotor isunbalanced by the relocation of liquid within the rotor thus causing therotor to rotate and bring a detonator in line with a firing train.

1 Claim, 7 Drawing Figures PIIIENIEDMARZO ma sum 1 OF 4 FIG. IA

SPIN

AXIS

INVENTORS M ATTORNEY PATENTEDMARZO ms 3.721.195

sum 2 a; 4

SPIN AXIS INVENTORS WERNER H. EGU

JORN sevsnson BY ATTORN v PATENTEU M820 I975 SHEET 3 0F 4 FIG; 3A

SPIN AXIS FIG. 38

PATENTEDHARZO ms 3. 721, 195 SHEET u 0F 4 INVENTORS WERNER H. EGLIASBJORN M. SEVERSON ATTORNEY LIQUID REVOLUTION COUNTER FOR FUZE ARMINGBACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention pertains to ammunition and explosive devices and, moreparticularly, to fuzes utilizing the centrifugal force of a spinningprojectile.

2. Description of the Prior Art The function of a safing and armingdevice is to ensure a safe condition in a projectile when it is handled,stored, and fired, and to reliably remove the safing feature and arm theprojectile when it has reached a safe distance from the deliveryvehicle. This is accomplished by a device designed to respond to forcesin the environment of the projectile to remove a barrier or barriers toexplosive train function.

Projectile ballistics start with setback forces within the projectileon, firing. The projectile quickly picks up spin as it moves over therifling in the gun barrel. Then, as it leaves the barrel, setback forcesabate and they are replaced by aerodynamic drag, which reduces thevelocity, and to a lesser degree the spin, of the projectile.

Generally, sensing at least two environments, such as setback and spin,is required to arm the projectile. The conventional method of arming isto utilize mechanical means. Mechanical fuzes tend to be relativelycomplex due to the number of parts and the tolerances imposed by sizerequirements. The dual environment requirement satisfies a high safetyfactor, but reliability decreases and cost increases with complexity.

BRIEF SUMMARY OF THE INVENTION In accordance with the invention, arevolution counter for fuze arming is provided for counting the numberof revolutions which a projectile has experienced subsequent to firing.The revolution counter consists of a liquid-containing rotor mountedwithin the projectile. The rotor has two compartments, one of which isnear the nose of the projectiles and the other. This forward compartmenthas a portion located further from the spin axis than is the furthermostportion of the rearward compartment from the spin axis. Connecting thetwo compartments is a drainage vent which allows the liquid to move intothe rearward compartment upon the projectile experiencing setback force.Also connecting the two compartments is a timing conduit which leadsfrom a point within the rearward compartment further from the spin axisthan is the drainage vent.

Upon furthest firing, the liquid will be forced into the rearwardcompartment, where, upon experiencing spin forces, the liquid will moveto the portion of the rearward compartment which is furthest from thespin axis. The liquid will then begin to squirt out of the timingconduit. The total flow of liquid from the rearward compartment, throughthe conduit, and, into the forward compartment is dependent upon thenumber of turns of the projectile. After a predetermined number ofturns, enough liquid has escaped from the rearward compartment andarrived at the forward compartment to change the center of gravity ofthe rotor and thus cause it to rotate.

Accordingly, an object of the present invention is to provide a solelyliquidic-contained rotor for a safing and arming mechanism.

Similarly, it is an object of the present invention to provide a devicewhereby the liquid within the fuze does actual work as opposed to merelybeing provided to constitute a barrier.

It is an additional object to provide a safing and arming mechanismwhereby the arming is dependent upon the number of revolutions of theprojectile in which it is housed.

Another object of the invention is to provide a safe, highly reliable,and non-complex safing and arming mechanism.

Another object is to provide a fuze which receives its energy directlyfrom ballistic environmental forces and, therefore, requires no storedenergy.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is an illustration of apreferred embodiment of the invention shown in a projectile head;

FIG. 1B is a view along AA ofFIG.1A;

FIG. 2 shows liquid rotating about an axis;

FIG. 3A is a second embodiment and is a view along B-B of FIG. 38;

FIG. 3B is the second embodiment and is a view along CC of FIG. 3A;

FIG. 4A is an illustration of a third embodiment of the invention; and

FIG. 4B is a top view of FIG. 4A.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1A, a rotor 11is shown within a projectile head 12. FIG. 1B shows a view along AA ofFIG. 1A and isolates rotor 11. Rotor 11 is discshaped and has acylindrical internal forward compartment l3 (forward with respect to theprojectile nose) and cylindrical internal rearward compartment 14 whichcompartments are separated by a wall 15. Compartment 13 has a portion 16which is located further from the spin axis than is the furthermostportion 17 of compartment 14. Portion 16 must be large enough to holdenough liquid to unbalance the rotor. A portion 18 is provided tobalance the rotor but is blocked from compartment 13 by a separator 19.Wall 15 has a drainage vent 20 connecting an aperture 21 withincompartment 13 with an aperture 22 in compartment 14. Wall 15 also has atiming conduit 23 located near the furthermost portion 17 of compartment14 and connecting an aperture 24 in the rearward compartment 14 with anaperture 25 in the forward compart ment 13. Aperture 24 is locatedfurther from the spin axis than is aperture 22 to ensure thatcentrifuged liquid exits through the timing conduit 23 rather than thedrainage vent 20.

Centrifugal locks 26 are provided to restrain the rotor. The rotorrotates about pins 27 upon being unbalanced. A boss 28 rides in a groove29 to restrain the total movement of the rotor 11.

Also shown is striker 30, which, upon experiencing ground impact,strikes the detonator 31 which in turn initiates booster 32. It is to beunderstood that the firing train arrangement is quite flexible. Forinstance, detonator 31 could be just a hole which either a striker or anexplosive utilizes in order to reach an explosive located at booster 32.

A liquid 33 is shown centrifuged against the walls of compartment 14.The liquid to be used within the rotor should possess the properties ofinviscidity, and high density, and in addition have low viscosity downto 65F and up to 160F. The properties of viscosity and high density varygreatly. The property of high density is needed since it causes a moresignificant change in the center of gravity of the rotor when it moves.Low viscosity is needed to ensure that viscosity forces are negligibleas compared with inertial forces. Liquid Freon E3 sold under thetrademark Freon by E. l. Du- Pont deNemours, having a density of 1.72gm/cc and a viscosity of 1.35 cs at +77F, and liquid Halocarbon l5 soldunder the trademark l-lalocarbon by Halocarbon Products Corporation,having a density of 2.75 gm/cc and a viscosity of 0.55 cs at 77F, willsatisfy the above requirements.

In operation, setback forces all of liquid 33 down through vent and intocompartment 14. As setback abates, due to the projectile leaving the gunbarrel, and the spin speed reaches its terminal value, the liquid 33becomes centrifuged against the walls of the compartment 14 forming ahollow cylinder pressing against the cylindrical walls of compartment14. This can be seen in FIG. 1A.

However, there is now a radial pressure gradient in the liquid whichcauses the liquid 33 to flow out of the timing conduit 23 and becentrifuged into portion 16. The rotor geometry, liquid flow speed, andliquid viscosity are selected to ensure inviscid flow. It is importantto note that even if aperture 24 is located at portion 17, prior tounbalancing the rotor, the timing conduit 23 cannot follow a path thattakes the liquid 33 closer to the spin axis than the inside diameter ofthe centrifuged liquid within compartment 14, or else the liquid willnot enter compartment 13 but will occupy compartment 14 and conduit 23up to the point of force equilibrium. This is true for all embodimentsof the invention.

With the spin rate sufficiently high, centrifugal locks 26 move outward.When a sufficient quantity of liquid has arrived at portion 16, thecenter of gravity of the rotor will have shifted sufficiently to rotatethe rotor about pins 27 thus moving the detonator 31 in line with thestriker 30 and the booster 32. It is to be noted that it is notnecessary that the rotor rotate about a pivot. For example, the rotorcould slide about an infinite radius to arm.

The unbalancing of the rotor is dependent upon the number of projectileturns and independent of the spin rate. Utilizing this fact, the rotorcan be built which will arm after a predetermined number of turns. Forexample, it has been found that for most military projectiles 26 turnswill ensure that the projectile is a safe distance from the launch siteprior to arming. Reference to FIG. 2 will aid in understanding thedependence upon the number of projectile turns. FIG. 2 shows a quantityof liquid contained in a container spinning about an axis. For inviscidflow, Bernoullis Equation teaches that Where p is the fluid density andV is the exit velocity from the nozzle.

Also, it is known that the pressure difference c A,,) due to centrifugalforce is eliminating A yields,

where w is the rate of rotation.

Also, the velocity Vcan be expressed as where Q is the quantity of fluidcontained in the container and A is the nozzle area.

Also,

where 0 is the angle traversed about the projectile axis.

Substitution gives But since R, is a function of Q only, and since A andR are constants to be selected by the designer, upon integrating we getQ F(0).

The above analysis is valid only if the flow is inviscid. If flow isviscid, the A,, would be a function of the unsquared exit velocity sothat the device would then be dependent upon spin speed.

In order to select the proper size for the revolution counter describedin FIG. 1A and 1B, the following analysis can be made. Let the diameterof the cylinder be D let the diameter of the core of the hollow cylinderof liquid be D Then, the hydrostatic pressure difference across thetiming conduit is:

(p(/( w 2 l( 1/ 2 l The quantity of liquid in the rearward compartmentis:

Q 0/ r/ l Where L is the axial length of the lower chamber, to is theangular spin speed.

Also we have:

where V is the speed at which inviscid liquid squirts through the timingorifice.

But,

Where A is the orifice area, and (dQ)/dt is the rate of depletion of thefluid in the rearward compartment.

I herefore:

pa) 2 Q dt dQ A... 3 WE But since w=d0/dt, this reduces to Thisintegrates to Hence, if arming is desired after N projectilerevolutions, and if the value of Q for which the center of gravitydisplacement makes the device rotate and arm is EQ (0 s' E l), thedevice is designed so that:

i.e., E= I NA V'nLQ For example, arming will occur after 26 revolutionarming with:

Q,,=0.0266 in L 0.5 in

A 0.0025 in The foregoinganalysis is valid only for the geometry cited,but can readily be modified for other geometries, giving the samegeneral result:

Arming M0) In those cases where analysis is too difficult,experimentation will readily determine the values needed for therelevant parameters.

Referring describes to FIGS. 3A and 38, a second embodiment of theinvention is shown. This embodiment is shown isolated from theprojectile which must be a clockwise spinning projectile. Thisembodiment described a liquid filled rotor which upon becomingunbalanced rotates horizontally or, as seen relative to the projectile,around an axis parallel to the spin axis. FIG. 3A is a view along B-B ofFIG. 3B, and FIG. 3B is a view along C-C of FIG. 3A.

Rotor 40 is shown upon a movable plate 41. Rotor 40 contains a forwardcompartment 42 and a rearward compartment 43, which compartments areseparated by a wall 44. Compartment 42 has a portion 45 which is locatedfurther from the spin axis than the furthermost portion 46 ofcompartment 43. Portion 45 must be large enough to hold enough liquid tounbalance the rotor. Wall 44 has a drainage vent 47 and also two timingconduits 48 (shown in FIG. 3A, but by dotted line in FIG. 38) locatednear the furthermost portion 46 of compartment 43 and connecting anaperture 49 in the rearward compartment with an aperture 50 in theforward compartment. Drainage vent 47 connects an aperture 51 incompartment 43 with an aperture 52 in compartment 42. Aperture 49 islocated further from the spin axis than is aperture 51.

Restrainer 53 prevents the rotor from rotating the plate 41 in acounter-clockwise direction (as seen in FIG. 3A) about a pivot 54. Therotor rotates about pivot 54 upon becoming unbalanced and causes plate41 to rotate to a stop 55 and thus move detonator 56 in line with theremainder of the firing train.

In this embodiment a liquid 57 is contained and is shown in dotted linein FIG. 3A centrifuged within rearward compartment 43 as would occurupon sensing centrifugal force.

In operation, setback forces all of the liquid 57 down into compartment43. As setback forces abate, and the spin speed reaches its terminalvelocity, the liquid 57 will become centrifuged against the walls of thecompartment 43 as shown in FIG. 3A. This distribution of the liquid massin the lower'compartment causes a counterclockwise torque about thepivot 54 which holds the rotor against the restrainer 53.

However, the centrifugal pressure gradient within the liquid 57 causesit to flow through the timing conduit 48 and into the forwardcompartment 42. The liquid 57 flowing into the forward compartment 42disposes itself in a hollow semi-cylinder located further from the spinaxis than was the liquid when it was in the rearward compartment 43.When enough liquid has flowed into the forward compartment 42, the shiftof the liquid mass distribution to the right side of the rotor willcause a clockwise torque about the pivot 54. This torque will rotate theentire rotor 41 about the pivot 54 and thus move detonator 56 in line.Once again it is not necessary that the rotor rotate about a pin. Itcould slide to a new position upon becoming unbalanced.

The same type of mathematical analysis as that used for the firstembodiment can be used to design the second embodiment for arming aftera predetermined number of revolutions.

Shown in FIGS. 4A and 4B is a third embodiment of the invention,isolated from a clockwise spinning projectile. FIG. 4B is a top view ofFIG. 4A. A rotor 60 is shown containing a forward compartment 61 and arearward compartment 62. It can be seen by examining FIG. 4A that thefloor 63 of the rotor slants upward from the rearward compartment 62 tothe forward compartment 61. Separating the two compartments is a wall64. Compartment 61 has a portion 65 which is located further from thespin axis than is the furthermost portion 66 of compartment 62. Portion65 must be large enough to hold enough liquid to unbalance the rotor.Wall 64 has a drainage vent 67, and also a timing conduit 68 locatednear the furthermost portion 66 of compartment 62 and connecting anaperture 69 in the rearward compartment to an aperture 70 in the forwardcompartment. Drainage vent 67 connects an aperture 71 in compartment 62with an aperture 72 in compartment 61. Aperture 69 is located furtherfrom the spin axis than is aperture 71.

A restrainer 73 prevents the rotor from rotating counterclockwise aboutthe pivot 74. A stop 75 is provided to restrain the total movement ofthe rotor in a clockwise direction. Also shown is a blocker plate 76which blocks the output of a detonator (not shown) from the remainder ofthe firing train (not shown) until the rotor has rotated to itsclockwise position.

A liquid 77 is shown centrifuged against the walls of compartment 62.

In operation, setback forces all of the liquid 77 down the rotor floor63, through vent 67, and into compartment 62. As setback forces fade outand the spin speed reaches its terminal value, the liquid 77 becomescentrifuged against the walls of the compartment 62, and assumes theshape shown in FIG. 48.

However, there is now a radial pressure gradient in the liquid whichcauses the liquid to flow out of the timing conduit 68 and travel intothe compartment 61. When a sufficient quantity of liquid has arrived atcompartment 61 and assumed the furthermost portion 65 from the axis, theshift of the liquid mass distribution to the right side of the devicewill cause a clockwise torque about the pivot 74. This torque willrotate the entire rotor around the pivot 74 and thus move the blockerplate 76 out of line with the firing train.

While this invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives,modifications, and variations will be apparent to those skilled in theart in light of the foregoing description. Accordingly, it is intendedto embrace all such alternatives, modifications and variations that fallwithin the spirit and scope of the claims I claim as my invention:

1. In a projectile which rotates about an axis, a liquid-containingrotor for bringing a detonator in line with a booster and the means forinitiating said detonator, comprising:

a rotor containing said detonator, said rotor defining a forwardcompartment and a rearward compartment, said forward compartment havinga portion located further from said axis than is the furthermost portionof said rearward compartment from said axis, said portion of saidforward compartment being large enough to hold enough liquid tounbalance the rotor, said rotor having a timing conduit leading from afirst aperture near said furthermost portion of said rearwardcompartment to a first aperture in said forward compartment following apath that is not closer to said axis than centrifuging liquid withinsaid rearward compartment prior to rotor unbalancing, said rotor alsohaving a drainage vent leading from a second aperture in said rearwardcompartment, said second aperture in said rearward compartment beingnearer said axis than is said first aperture in said rearwardcompartment; and

means restraining said rotor from rotating until a predeterminedrotational speed of said projectile;

whereby said rotor is responsive to the movement of said liquid fromsaid rearward compartment to said forward compartment, and thus thenumber of revolutions of said projectile, for rotating said rotor thusbringing said detonator in line.

1. In a projectile which rotates about an axis, a liquidcontaining rotorfor bringing a detonator in line with a booster and the means forinitiating said detonator, comprising: a rotor containing saiddetonator, said rotor defining a forward compartment and a rearwardcompartment, said forward compartment having a portion located furtherfrom said axis than is the furthermost portion of said rearwardcompartment from said axis, said portion of said forward compartmentbeing large enough to hold enough liquid to unbalance the rotor, saidrotor having a timing conduit leading from a first aperture near saidfurthermost portion of said rearward compartment to a first aperture insaid forward compartment following a path that is not closer to saidaxis than centrifuging liquid within said rearward compartment prior torotor unbalancing, said rotor also having a drainage vent leading from asecond aperture in said rearward compartment, said second aperture insaid rearward compartment being nearer said axis than is said firstaperture in said rearward compartment; and means restraining said rotorfrom rotating until a predetermined rotational speed of said projectile;whereby said rotor is responsive to the movement of said liquid fromsaid rearward compartment to said forward compartment, and thus thenumber of revolutions of said projectile, for rotating said rotor thusbringing said detonator in line.